Modes of Transmission

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Modes of Transmission
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Transmission Definitions

• Transmission can be generally classified as
• Airborne pathogens that are in the air that are
  breathed in.
• Waterborne pathogens that are in water supplies
  that are drank in.
• Foodborne pathogens that are in food that is
  eaten.
• The following are ways that pathogens can enter
  the body and may or may not fall under the above
  three general categories.

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1) Insect-Borne Vectors

• Insects form a large portion of pathogen vectors
  because many of them are hematophagic, meaning
  they feed on blood at some point in their
  lifecycle.
• Mosquitoes, ticks, lice, fleas and some flies are
  examples of insect vectors.
• Other animals can be vectors as well, but not as
  common as insects (i.e. rats, mice, cows, deer).

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1) Insect-Borne Vectors

• The pathogen is picked up by the vector insect at
  some other point and transferred to the human
  host in many ways, each circumvents the first
  line of defense, the skin.

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1) Insect-Borne Vectors

• Some insect vectors pierce the skin with a
  specialized mouthpart (i.e. mosquito).
• Others simply bite the skin and create a pool of
  blood (i.e. black fly)
• The triatomine bugs, responsible for passing on
  the protist which causes Chagas disease,
  defecates the pathogen out while it feeds and the
  host rubs it into the wound in response to the
  bite!
• All these methods pass the pathogen right into
  the bloodstream where it can do the most damage.

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2) Droplet Contact

• Many pathogens require the air to provide a
  pathway to infect other hosts.
• The pathogen particles travel from one host to
  another through the air in a cough or a sneeze.
• The pathogens get in the body through the
  respiratory tract.

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3) Direct Contact

• Pretty straightforward
• An infected person with outward signs of
  infection makes physical contact with an
  unaffected individual and passes on the pathogen.
• In many cases the contact is sexual.

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4) Indirect Contact

• An infected individual touches a surface and
  leaves the pathogen on that surface.
• An unaffected individual touches the same surface
  later on and picks up the pathogen.
• The pathogen can then enter into the body (i.e.
  hand in mouth).

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5) Fecal-Oral

• An affected person does not wash their hands
  after going to the bathroom and transfers a
  pathogen to a food source that is then eaten.
• Can also happen if raw sewage mixes with drinking
  water.
• Most foodborne pathogens are through this method
  of transmission.

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6) Vertical Transmission

• This is when an affected mother passes the
  pathogen on to her developing fetus through her
  bloodstream.
• Usually sexually transmitted diseases (STDs) like
  HIV, Hepatitis B, Syphilis, etc

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7) aerosol Transmission

• Not a natural way for a pathogen to be released.
• This is where a pathogen is released in tiny
  droplets of water that hang in the air for long
  periods of time.
• Considered bioterrorism.
• The USA has BioWatch to analyze air samples and
  ensure terrorists have not released pathogens
  into the air over a major city center.

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Exciting news item

• http//www.cnn.com/2013/03/03/health/hiv-toddler-c
  ured

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Homework

• What the three lines of defense a pathogen must
  break through in order to cause illness in a
  human.
• Indicate 5 places on the human body that a
  pathogen may try to enter.
• For each type of transmission, indicate two
  pathogens (as specific as possible) that follow
  that method of infection.
• Other than vertical transmission, indicate one
  way you could protect yourself against each type
  of transmission.